This application is based on Japanese Patent Application No. 2001-213059 filed in Japan on Jul. 13, 2001, the entire content of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a rear projection optical system. More concretely, the invention relates to the rear projection optical system which is suitable to a rear projection apparatus (for example, a rear projection television) for enlarging and projecting a display image of a display panel (for example, a liquid crystal panel) on a screen from a rear side.
2. Description of the Related Art
FIGS. 7(A) and 7(B) are a front view and a right side view of a rear projection television into which a rear projection optical system of a conventional example is incorporated. This rear projection television has an illuminating optical system (1), a projection lens (2), a deflection mirror (3), a curved mirror (4), a rear mirror (5) and a screen (6). In this rear projection optical system, a display panel (not shown) is illuminated by the illuminating optical system (1) provided below the center of the screen (6), and a display image of the illuminated display panel is enlarged and projected onto the screen (6) by the projection lens (2) and the like. At this time, a projection light flux emitted from the projection lens (2) is reflected successively by the deflection mirror (3), the curved mirror (4) and the rear mirror (5) so as to reach the screen (6).
In the structure of the rear projection optical system shown in FIG. 7, a size (H) of a portion below the screen (6) (so-called portion chin or lower jaw) and a size of depth (D) becomes large, and thus the entire equipment becomes large.
The present invention is devised in order to solve the above problem, and its object is to provide a rear projection optical system which can achieve miniaturization and thinning of a rear projection apparatus.
To achieve the above mentioned object, a rear projection optical system corresponding to one aspect of the present invention installed at a rear side of a screen of a rear projection apparatus comprises: a display panel; an illuminating optical system for illuminating the display panel, the illuminating optical system being decentered from a screen center in both of a horizontal direction and a vertical direction; and a projection optical system, decentered from the screen center in the vertical direction, for projecting a display image on the display panel projected by the illuminating optical system onto a screen through a rear mirror positioned at a position that is the center of the screen. The projection optical system includes a dioptric system, a deflection mirror, and a curved mirror in this order from the display panel to the rear mirror, and the curved mirror is decentered from the screen center in the vertical direction but centered against the screen center in the horizontal direction.
In the above mentioned structure, when the rear projection apparatus is observed from one side thereof in the vertical direction, the illuminating optical system is provided at a position so as not to overlap with a light flux from the projection curved mirror to the rear mirror.
Further to or separately from the above, in the rear projection apparatus corresponding to one aspect of the invention, when the rear projection apparatus is observed from one side thereof in the vertical direction, the illuminating optical system may be provided at a position so as to at least partly overlap with a light flux from the rear mirror to the screen.
Further to or separately from the above, in the rear projection apparatus corresponding to one aspect of the invention, when observed from the one end of the screen in the horizontal direction, the illuminating optical system may be provided at a position so as to at least partly overlap with a light flux from the projection curved mirror to the rear mirror.
Further to or separately from the above, in the rear projection apparatus corresponding to one aspect of the invention, the illuminating optical system may comprise a plurality of optical element including a light source. In this case, the light source may mostly be centered in the horizontal direction among the plurality of optical elements.
Further to or separately from the above, in the rear projection apparatus corresponding to one aspect of the invention, the dioptric system may be provided so that an optical axis thereof is parallel to the screen.
Further to or separately from the above, in the rear projection apparatus corresponding to one aspect of the invention, the curved mirror may have a negative optical power to enlarge a light flux of the display image.